Secondary Electron Emission from a Charged Dielectric

Charges on the surface of fluorinated-ethylene-propylene affect its secondary electron emission coefficient. Measurements with impact energies exceeding that energy which causes peak emission have been made in regions where the local electric field produced by the surface charge is normal to the surface and in regions where it is oblique. The surface of the 6-mm wide specimen was charged to either 6 or 10 kV. Because the impinging primary beam was deflected by the charged specimen, numerical modeling was used to predict the beam's impact energy E, impact angle θ, and the impact point. The formula (E0/E) ncosθ predicts the coefficient in the region of normal field up to 60° although E0 depends upon the electric field and also on the history of the specimen. Near the edges where the field is obliquie, the measured coefficient departs significantly from what the formula predicts.